The present invention relates generally to completion operations performed in subterranean wells and, in an embodiment described herein, more particularly provides a gravel packing apparatus and methods.
Downhole assemblies utilized in formation fracturing and/or gravel packing operations in subterranean wells typically include a sealing device, such as a packer specially designed for the purpose, a filtration device, such as a screen or slotted liner, and various other items of equipment for controlling fluid flow therethrough. In general, the packer is set in a wellbore of the well prior to commencement of fluid or slurry flow in the formation fracturing or gravel packing operation. In some cases, the assembly is sealingly engaged at its lower end with a sump packer set in the wellbore below a formation intersected by the wellbore.
It is usually the case that, after the completion operation is concluded, a production tubing string is connected to the assembly and the special purpose packer becomes, in effect, a production packer. Unfortunately, the special purpose packer is generally much more expensive than a normal production packer. Thus, the well operator is required to pay the higher cost of the special purpose packer even though, after the completion operation is concluded, all that is needed is a normal production packer. Therefore, it would be quite desirable to provide a packer which may be utilized in completion operations, such as formation fracturing and gravel packing, but which may be produced at or below the cost of a normal production packer.
Additionally, it is common for special purpose packers utilized in formation fracturing and gravel packing operations to be provided with slips for anchoring the packer to the wellbore (or anchoring to protective casing lining the wellbore). These slips are generally formed of hardened material, so that they are able to bite into and thereby deform the inner surface of the wellbore. As used herein, the term "anchoring" is used to describe this operation whereby one or more elements of a packer or other sealing device bite into the inner surface of the wellbore or wellbore lining. As used herein, the term "setting" is used to describe an operation in which a packer or other sealing device is sealingly engaged with the inner surface of the wellbore or wellbore lining. Additionally, if the packer or other sealing device includes elements, such as slips, for biting into the inner surface of the wellbore or wellbore lining, the term "setting" also includes anchoring.
Unfortunately, the slips, or other anchoring devices, are difficult to mill when subsequent operations require removal of the packer from the wellbore. Of course, the packer may be provided as a retrievable type, wherein the slips are retractable for ease of removal of the packer, but such retrievable packers typically cost more than a normal production packer, due to the added expense of the retrieving mechanism. Thus, it would be desirable to provide the packer for use in the completion operation with the packer being free of slips for anchoring the packer to the wellbore. Additionally, it would be desirable to provide the packer made partially or wholly of easily millable materials, such as aluminum, plastic, etc.
To prevent axial movement of the assembly during, and subsequent to, the completion operations, the assembly could be attached to the sump packer, or abutted against a surface in the wellbore, such as the bottom of the wellbore. Therefore, it would also be desirable to provide the assembly having an attachment member or an abutment member connected thereto. Furthermore, it would be desirable for the packer to be settable in the wellbore by application of a compressive axial force thereto, the force being resisted by the sump packer or the wellbore surface contacted by the abutment member.
In addition, the above considerations are applicable, with appropriate modifications, to other sealing devices used in subterranean wells. For example, it would be desirable to provide a casing patch which is free of slips for anchoring the casing patch to the wellbore or wellbore lining, which is made partially or wholly of easily millable materials, which has an attachment member or an abutment member connected thereto, and/or which is settable by application of a compressive axial force thereto.